Electron-Acoustic Phonon Energy Loss Rate in Multi-Component Electron Systems with Symmetric and Asymmetric Coupling Constants

We consider electron-phonon (\textit{e-ph}) energy loss rate in 3D and 2D multi-component electron systems in semiconductors. We allow general asymmetry in the \textit{e-ph} coupling constants (matrix elements), i.e., we allow that the coupling depends on the electron sub-system index. We derive a multi-component \textit{e-ph}power loss formula, which takes into account the asymmetric coupling and links the total \textit{e-ph} energy loss rate to the density response matrix of the total electron system. We write the density response matrix within mean field approximation, which leads to coexistence of\ symmetric energy loss rate $F_{S}(T)$ and asymmetric energy loss rate $F_{A}(T)$ with total energy loss rate $F(T)=F_{S}(T)+F_{A}(T)$ at temperature $T$. The symmetric component F_{S}(T) $is equivalent to the conventional single-sub-system energy loss rate in the literature, and in the Bloch-Gr\"{u}neisen limit we reproduce a set of well-known power laws$F_{S}(T)\propto T^{n_{S}}$, where the prefactor and power$n_{S}$depend on electron system dimensionality and electron mean free path. For$F_{A}(T)$we produce a new set of power laws F_{A}(T)\propto T^{n_{A}}$. Screening strongly reduces the symmetric coupling, but the asymmetric coupling is unscreened, provided that the inter-sub-system Coulomb interactions are strong. The lack of screening enhances $F_{A}(T)$ and the total energy loss rate $F(T)$. Especially, in the strong screening limit we find $F_{A}(T)\gg F_{S}(T)$. A canonical example of strongly asymmetric \textit{e-ph} matrix elements is the deformation potential coupling in many-valley semiconductors.Comment: v2: Typos corrected. Some notations changed. Section III.C is embedded in Section III.B. Paper accepted to PR

Pseudo Jahn-Teller Effect In The Origin Of Enhanced Flexoelectricity

The controversy between the theory and experiment in explaining the origin of enhanced flexoelectricity is removed by taking into account the pseudo Jahn-Teller effect (PJTE) which, under certain conditions, creates local dipolar distortions of dynamic nature, resonating between two or more equivalent orientations. The latter become nonequivalent under a strain gradient thus producing enhanced flexoelectricity: it is much easier to orient ready-made dipoles than to polarize an ionic solid. For BaTiO3, the obtained earlier numerical data for the adiabatic potential energy surface in the space of dipolar displacements in the Ti centers were used to estimate the flexoelectric coefficient integral in the paraelectric phase in a one-dimensional model with the strain gradient along the [111] direction: integral = -0.43 X 10(-6) Cm-1. This eliminates the huge contradiction between the experimental data of integral similar to mu Cm-1 for this case and the theoretical predictions (without the PJTE) of 3-4 orders-of-magnitude smaller values. Enhanced flexoelectricity is thus expected in solids with a sufficient density of centers that have PJTE induced dipolar instabilities. It explains also the origin of enhanced flexoelectricity observed in other solids, noticeable containing Nb perovskite centers which are known to have a PJTE instability, similar to that of Ti centers. The SrTiO3 crystal as a virtual ferroelectric in which the strain gradient eases the condition of PJTE polar instability is also discussed. (C) 2015 AIP Publishing LLC.Institute for Theoretical Chemistr

Galactic cluster winds in presence of a dark energy

We obtain a solution for the hydrodynamic outflow of the polytropic gas from the gravitating center, in presence of the uniform Dark Energy (DE). The antigravity of DE is enlightening the outflow and make the outflow possible at smaller initial temperature, at the same density. The main property of the wind in presence of DE is its unlimited acceleration after passing the critical point. In application of this solution to the winds from galaxy clusters we suggest that collision of the strongly accelerated wind with another galaxy cluster, or with another galactic cluster wind could lead to the formation of a highest energy cosmic rays.Comment: 13 pages, 7 figure

Current fluctuations near to the 2D superconductor-insulator quantum critical point

Systems near to quantum critical points show universal scaling in their response functions. We consider whether this scaling is reflected in their fluctuations; namely in current-noise. Naive scaling predicts low-temperature Johnson noise crossing over to noise power $\propto E^{z/(z+1)}$ at strong electric fields. We study this crossover in the metallic state at the 2d z=1 superconductor/insulator quantum critical point. Using a Boltzmann-Langevin approach within a 1/N-expansion, we show that the current noise obeys a scaling form $S_j=T \Phi[T/T_{eff}(E)]$ with $T_{eff} \propto \sqrt{E}$. We recover Johnson noise in thermal equilibrium and $S_j \propto \sqrt{E}$ at strong electric fields. The suppression from free carrier shot noise is due to strong correlations at the critical point. We discuss its interpretation in terms of a diverging carrier charge $\propto 1/\sqrt{E}$ or as out-of-equilibrium Johnson noise with effective temperature $\propto \sqrt{E}$.Comment: 5 page

Frequency dependent third cumulant of current in diffusive conductors

We calculate the frequency dispersion of the third cumulant of current in diffusive-metal contacts. The cumulant exhibits a dispersion at the inverse time of diffusion across the contact, which is typically much smaller than the inverse $RC$ time. This dispersion is much more pronounced in the case of strong electron-electron scattering than in the case of purely elastic scattering because of a different symmetry of the relevant second-order correlation functions.Comment: 8 pages, 4 figure

On chaotic behavior of gravitating stellar shells

Motion of two gravitating spherical stellar shells around a massive central body is considered. Each shell consists of point particles with the same specific angular momenta and energies. In the case when one can neglect the influence of gravitation of one ("light") shell onto another ("heavy") shell ("restricted problem") the structure of the phase space is described. The scaling laws for the measure of the domain of chaotic motion and for the minimal energy of the light shell sufficient for its escape to infinity are obtained.Comment: e.g.: 12 pages, 8 figures, CHAOS 2005 Marc